A microelectronic device may include a capacitor in the interconnect region. The lower plate of the capacitor may be a metal layer that is part of an interconnect level, to reduce cost and complexity of the microelectronic device. The interconnect level may include interconnects of etched aluminum. There are several desirable characteristics of the capacitor. A first desirable characteristic is high capacitance density, which may be expressed as a high ratio of the capacitance to the area occupied by the capacitor. A second desirable characteristic is low variations in the capacitance over the range of voltages applied to the capacitor. A third desirable characteristic is high reliability, which may be understood as meeting the first and second desirable characteristics for an expected operational lifetime of the microelectronic device under the expected operating conditions of the microelectronic device. A fourth desirable characteristic is compatibility of the capacitor fabrication operation with the patterning steps used to form the etch mask for the interconnect level containing the lower plate of the capacitor. Such a desirable characteristic places limitations on the thickness and composition of the capacitor dielectric layer over the lower plate. Attaining all four desirable characteristics simultaneously has been problematic.